The present invention relates to a system that removes heat and moisture from around the body of an individual wearing soft body armor.
With the increasing number and sophistication of threats to law enforcement officers today, the use of soft body armor is more and more critical. Evidence clearly shows that wearing body armor saves lives. Yet, many law enforcement officers choose not to wear soft body armor. Of the reasons officers use when choosing not to wear soft body armor, comfort, weight, fit, and heat build-up top the list. The discomfort, according to the officers, of wearing soft body armor outweigh the risks they perceive of getting shot.
While some of these complaints may be related to overall weight, fit or improper adjustment, complaints that armor makes the officers feel hot are not principally fit-related. The basic problem is that the ballistic protective layers are good thermal insulators and also block the ability to remove moisture. The impermeable surface area that a soft body armor vest covers is significant compared with the total area of the wearer""s skin. Just six plies of fabric, waterproofed or not, are enough to block the evaporation of perspiration. The National Institute of Justice has issued Threat Levels I-IV in Standard 0101.04. This establishes six formal armor classification types as well as a seventh special type.
Threat Level II vests contain at least seven ballistic layers. Thus, it is safe to say that any soft body armor vest, regardless of level or waterproofing, will block perspiration. The weight added to the vest due to perspiration not only places an extra load on the wearer, but the moisture can degrade the ballistic properties of the soft body armor. The vest, therefore, imposes a true cost to the wearer in terms of his body""s ability to cool itself.
While the industry has made major improvements over the past decade in overall weight and flexibility of the ballistic fabrics used, heat build-up and moisture retention have not been adequately addressed.
What is needed is a high-thermal-conductivity and moisture-wicking system that is either added to or integrated into a soft body-armor vest wherein heat and moisture are moved away from the body.
The present invention utilizes advanced materials, such as high thermal-conductivity graphite fibers and/or other high thermal-conductivity materials (metallic or non-metallic), to act as heat pipes, or paths, around body armor in order to transfer heat away from the body. The present invention also incorporates advanced moisture-wicking materials around the body armor to keep moisture away from the body and the body armor. In another embodiment, the high thermal-conductivity materials are integrated through the body armor vest, as opposed to traversing around, the soft body armor vest in order to transfer heat away from the body.
The present invention removes heat by transporting it along high thermal-conductivity fibers from the body-vest interface to the external environment, where it is removed by simple radiation and convection heat loss from the exterior of the vest. That is, the high thermally conductive fibers traverse the armor from an area next to the body to the exterior of the soft body armor vest through the inside of the vest. Because the external temperature influences the system behavior of the thermally conductive path, the higher the temperature humidity index (THI), the greater the difficulty in moving thermal energy out of the fibers and into the surrounding environment. After evaluating some basic heat transfer calculations, it became apparent that the required volume of conductive fibers of a given density, or more specifically the weight, needed to transport sufficient thermal energy would be larger than desired. To reduce the volume/weight of required fibers, the present invention uses the same process the body uses, namely, evaporative cooling. By using the perspiration that is currently generated under a vest, the present invention can improve the thermal coupling to the conductive fibers, create additional thermal capacity, and provide a cooling action through evaporation.
The present invention also utilizes a dual-faced overvest comprised of advanced moisture-wicking materials in order to pull moisture from the body of the wearer and from the body armor vest. Pulling moisture away from the body allows for a more comfortable experience by the wearer of the soft body armor vest. Pulling moisture away from the body armor vest minimizes any moisture induced mechanical effects on the ballistic cloth used in the body armor. The overvest acts like a wick, pulling moisture from the overvest/body interface and the overvest/body armor interface. The moisture is then moved to the outside surface of the overvest, where it can be dissipated by evaporative cooling. Additionally, a wetted (moisture wicking) material is coupled with the thermally conductive fibers to enhance heat extraction from the wearer""s body. An evaporative cooling effect, which is a one-way phase change process that is similar to that of the human body, removes thermal energy from the conductive fibers at the external surface of the overvest dissipating the heat into the environment.